Mounting X Axis Drive Assemblies

The stepper/ball screw/support assemblies were ready to be attached to the machine. I used some K clamps across the width of the machine to use as supports to lay the assemblies on while I worked on aligning them properly.

First, I determined the front-back positioning. Moving the gantry to one end of travel, and the ball nut to the same end of its travel, I aligned the center of the ball nut coupler with the center point between the X linear bearing blocks. Then I clamped the assembly in place on that end. Moving the gantry and ball nut to the other end of their travel, I aligned the ball nut coupler with the center of the linear bearing blocks and measured the extra travel available on the ball screw. I split this measurement in half to allow equal space on both ends. I readjusted the position accordingly on both ends and clamped in place again.

To get the vertical alignment correct, I mounted the wooden piece to the ball nut coupler that would attach to the gantry. I moved one end up to the gantry, readjusting the k-clamp to set the new height, re-clamped the assembly, and then moved the ball nut and gantry back to the other end and repeated.

With everything in place and aligned, I unclamped one end at a time, applied wood glue, and re-clamped.

X Axis drive assembly clamped in place

I then repeated the whole process for the second X axis drive assembly on the other side of the machine. After the glue was dry and I reconfirmed the alignment was still correct, I glued the pieces in place that attach the ball nut couplers to the gantry.

Ball nut coupler attached to gantry

X Axis Alignment Fine Tuning

With the gantry mounted and the rails bonded in place, I was able to fine tune the X axis rail alignment.  I loosened the linear bearings on one rail and attached a dial indicator to the gantry at that same end, reading to the reference edge of the profile rail.  I ran the gantry back and forth to see how far out it was across the whole range of motion.  Most of the rail was within +/- 0.001” parallel to the opposite rail.  Toward the end there was a 6 inch section that was out by 8-10 thousandths.  I loosened those rail mounting bolts and applied some pressure on the rail by hand to bring it back to zero before re-tightening the rail.  After rechecking the whole rail it still needed some minor adjustments.  After a few rounds of this I am happy with the straightness.  Next up will be mounting the X axis drive assemblies.

Installing and Aligning X Rails

After placing the linear guide blocks on the X rails, I placed the gantry on top of them and proceeded to align everything. I spent a lot of time aligning the X axis rails. This included making sure they were parallel with each other and also that they were perpendicular to the Y axis rails on the gantry. I clamped together a few 24” squares to get the rails parallel and then placed some 1-2-3 blocks on top of them to check that the Y axis rails were perpendicular. I clamped the rails in place as I went to keep the alignment correct. Once I was happy with everything, I marked out where the linear bearings should be mounted to the gantry. I drilled the gantry and mounted the linear bearings, then installed the gantry on the rails again. I forgot to mention that I had previously found the balance point of the gantry using a thin piece of wood running the long way under the gantry. I marked that balance point on the base of the gantry on both ends and that became the center point between the two linear bearings.

Setup for aligning X axis rails

The alignment was double and triple checked prior to bonding the rails in place with the System Three adhesive epoxy. I still have some adjustment available in the rails to make fine adjustments with a dial indicator. I had previously used a chemical etch on these pieces of bar stock, but the epoxy should be applied very soon after the etching to get a good bond. I had let too much time pass and since I am experimenting and learning here, I decided to use the “wipe down with acetone” method for this to evaluate how the bond holds up compared to the other axes where I used the etching and sanding methods.

X Axis Frame Build

With the Z and Y Axis components almost complete, I couldn’t wait to get the X frame components built up. I cut all the plywood pieces on the tablesaw, then figured out what angle to cut out the MDF webs. Once I made one that fit well, I used the waste piece with a stop on my cross cut sled to quickly cut out the rest of the webs:

table saw setup for cutting angled webs

I assembled these in place on the machine base and once again glued everything up and used a lot of clamps. The waste pieces from the MDF webs came in handy again to make a squared up clamping surface.

clamped x axis frame side